This invention relates to utilization of communication channels between a central office telephone switch and a Law Enforcement Agency premises.
Law enforcement Agencies have found it necessary to intercept voice communications made for suspected illegal purposes. In the past, this was done through the process of attaching a wiretap to a telephone line which carried the telephone communication. Two types of interceptions are possible: the first, (Level 1), is used only for recording dialed information so that a record can be made of calls originated from a particular telephone; this has been enhanced in recent years to include the identity of a caller on an incoming call as well as the called party on outgoing calls. For cases in which probable cause is demonstrated to an appropriate judicial officer, a second level of interception is allowed in which a Law Enforcement Agency can actually listen and record the contents of the telephone communication.
The use of modern program controlled telephone switching systems, using digital telephone switching networks, has made it possible to implement the interception function more efficiently. At the same time, these systems have made it possible to have complex call configurations, which require that several telephone conversations from a single source may have to be monitored in order to intercept the key telephone communication.
In accordance with requirements specified by the Federal Communications Commission (FCC), a switching system is required to provide dedicated communications channels for each telephone customer whose communications are being intercepted at Level 2. In order to ensure that all of the communications from or to the targeted customer can be intercepted, a sufficient number of communications channels must be provided and dedicated between the central office switch serving the subject customer and a Law Enforcement Agency premises for the duration of the time that the customer""s line is being monitored. A problem with the prior art is that the number of such communications channels which must be dedicated for that purpose is uneconomically large, as discussed below.
In accordance with the requirements for surveillance service imposed by the FCC, several calls can be in progress at the same time for one subject customer. One simple example is the following: suppose that the subject customer requests that subordinates call him/her and have such calls forwarded to a third number. The subject customer can thus set up a large number of such calls, (especially if the subject customer has a sufficient number of subordinates), subject only to call forwarding limitations of the switch. Then, when the subject customer believes that the Communications Content Channels dedicated to monitoring his communications have been exhausted, the subject customer can make the critical call, which will then not be monitored unless the subject customer has mis-guessed the number of Communications Content Channels dedicated to surveillance of his telephone. This call scenario helps to explain why a large number of Communications Content Channels are required, at least for certain subject customers, and why even a large number of such channels may be inadequate in accordance with the teachings of the prior art.
Applicants have analyzed this situation and have recognized that the agents can usually tell which of several communications from, to, or otherwise associated with the subject customer, are likely candidates for carrying the desired communication to be intercepted. Even so, in the prior art, the dedicated communication channels carrying subject content that is deemed to be of no value for the purpose of a criminal investigation, cannot be disconnected and made available for use by other calls for the entire duration of the monitored call, even though the Law Enforcement Agent has shut off recording of the content of the monitored call. These communication channels are in use from the perspective of the switch, but not from the perspective of the Law Enforcement Agency; they are a wasted resource.
In accordance with this invention, an improvement is made over the teachings of the prior art by giving agents responsible for monitoring Level 2 communications the power to release a channel carrying one of the communications when that agent recognizes that the communication is not one of interest. In accordance with Applicants"" preferred embodiment, an agent can also request resumption of receipt of the content of the monitored call by making a reconnect request. Advantageously, the only channels that are required are the channels for carrying those communications that agents have identified as being of interest. Advantageously, arrangements by sophisticated lawbreakers to flood the communications channels for carrying their telephone communications to the Law Enforcement Agency premises can be defeated by this arrangement.
In accordance with one preferred embodiment of this invention, the signals from an agent to release a particular communications channel are sent over the signaling channel connecting the Law Enforcement Agency premises with the central office. This signaling channel can be an existing call data channel, or can be a separate administrative channel carrying only 1-way traffic for administrative messages. Advantageously, this provides a simple arrangement using currently installed equipment for communicating with the serving central office switch to release a particular communications channel.
In accordance with one preferred embodiment, each busy Communication Content Channel (CCC) is assigned a priority. This priority can be lowered if an Agent suspects that a communication is not of interest, so that a new higher priority communication can preempt the channel if no idle channels are available.